Regulators are commonly employed in fluid or gas distribution systems to control the pressure in the system downstream of the regulator. As is known, the pressure at which a typical gas distribution system supplies gas may vary according to the demands placed on the system, the climate, the source of the supply, and/or other factors. However, most end-user facilities equipped with gas appliances such as, for example, furnaces, and ovens, require the gas to be delivered in accordance with predetermined pressure parameters. Therefore, such distribution systems use gas regulators to ensure that the delivered gas meets the requirements of the end-user facilities.
Conventional gas regulators generally include a closed-loop control actuator or control assembly for sensing and controlling the pressure of the delivered gas. Many regulators use a pneumatic control assembly having a diaphragm and a sense tube, such as a Pitot tube, that extends into the outlet side of the regulator. The tube senses, for example, the pressure or other parameters in the downstream or outlet end of the regulator, and communicates that sensed parameter to the control assembly. Based on the sensed parameter, the control assembly makes any needed adjustments to the position of a control element, which then keeps the sensed parameter at a desired value or within an acceptable range.
FIG. 1 depicts an example of a conventional regulator device 100. The regulator device 100 generally includes an actuator 104 coupled to a valve body 108. The valve body 108 includes an inlet 112, an outlet 116, and a valve port 120 disposed between the inlet 112 and the outlet 116. The regulator 100 further includes a balanced port control assembly 122 that is mounted within the valve body 108 and that aims to improve the reaction of the regulator 100 to variations in the downstream pressure. The balanced port control assembly 122 includes, in relevant part, a control element 124 that is movable relative to the valve port 120.
The actuator 104 is coupled to the valve body 108 to ensure that the pressure at the outlet 116 of the valve 108, i.e., the outlet pressure, is in accordance with a desired outlet or control pressure. The actuator 104 is a diaphragm-based actuator and includes an actuator housing 128 containing a control assembly 132 for regulating the outlet pressure of the valve body 108 based on sensed outlet pressure. The control assembly 132 generally includes a diaphragm 136, a piston 140, and a control arm 144 operatively connected to a valve stem 148. The valve stem 148 is connected to the movable control element 124 of the balanced port control assembly 122, such that movement of the actuator 104 moves the control element 124 relative to the valve port 120. The control assembly 132 also includes a diaphragm chamber 152, which is in fluid communication with the outlet 116 via a sense tube 156. The sense tube 156 generally has a mounting end 157 in fluid communication with the diaphragm chamber 152, and a flared and open sensing end 158 disposed opposite the first end 157 and configured to sense the pressure at or in the outlet 116. The control assembly 132 further includes a control spring 160 in engagement with a top side of the control assembly 132 to offset the outlet pressure sensed by the diaphragm 136. Accordingly, the desired outlet pressure, which may also be referred to as the control pressure, is set by the selection of the control spring 160.
Generally speaking, the inlet 112 of the regulator device 100 receives gas from a gas distribution system, for example, and the outlet 116 delivers gas to an end-user facility such as a factory, a restaurant, an apartment building, etc. having one or more appliances. The actuator 104, via the control assembly 132, controls the position of the control element 124, and, consequently, gas flowing through the regulator device 100 flows into the inlet 112, through the valve port 120, and out the outlet 116 to the end-user facility, with the position of the control element 124 controlling the flow of gas through the device 100.
The control assembly 132 regulates the outlet pressure of the body 108 of the regulator device 100 based on the outlet pressure sensed in or at the outlet 116. More specifically, the diaphragm 136 senses the outlet pressure of the valve 108 and provides a response to move the valve stem 148 to open and close the valve 108. Specifically, the control assembly 132 includes a diaphragm support plate 164 coupled to the piston 140, which together move the position of the diaphragm 136, the control arm 144, the valve stem 148, and ultimately the control element 124. The open, sensing end 158 of the sense tube 156 senses the pressure in or at the outlet 116. If the sensed pressure is too low, the pressure in the diaphragm chamber 152 drops accordingly, by virtue of the flow communication provided by the mounting end 157 of the sense tube 156. Consequently, because the desired control pressure is applied to the piston side of the actuator 104, the pressure differential will cause the diaphragm 136 to move (to the right when viewing FIG. 1), which in turn moves the control element 124 (upward when viewing FIG. 1). This opens the valve port 120 more, thus increasing the pressure in the outlet 116. On the other hand, if the sensed pressure is too high, the pressure in the diaphragm chamber 152 is greater than the desired control pressure, and the pressure differential against the diaphragm 136 causes the diaphragm 136 to move (to the left when viewing FIG. 1), thus moving the control element 132 closer to the valve seat, which decreases the flow through the valve port 120.
As noted above, the sense tube 156 has a mounting end 157 and a flared and open sensing end 158. When fluid flows from the inlet 112, through the valve port 120, and out the outlet 116 over and past the sense tube 156, the sense tube 156 senses the pressure of the fluid at the flared and open sensing end 158. In high flow situations, however, there tends to be a large pressure drop across the flared and open sensing end 158, such that the sense tube 156 detects an artificially low pressure at the flared and open sensing end 158. In other words, the sense tube 156 senses a pressure that is lower than the actual pressure at the outlet 116. When the sense tube 156 communicates this artificially low pressure, via the mounting end 157, to the diaphragm chamber 152, this causes the diaphragm 136 to move (to the right when viewing FIG. 1) more than necessary or required, which in turn moves the control element 124 (upward when viewing FIG. 1) more than necessary and opens the valve port 120 more than necessary. Accordingly, the sense tube 156 may boost the downstream outlet pressure out of accuracy, thereby limiting the capacity of the regulator 100.